Panorama: Add border-image property from standard CSS

[vrad-exe]

What would this enhancement be for?

UI/UX

Describe your enhancement suggestion in more detail

As far as I can tell, the color of a border (or padding/margin) cannot be a gradient.

If the color is set directly within a border property, e.g:

border: 5px solid gradient( linear, 0% 0%, 100% 0%, from( #f1efe2 ), to( #716f64 ) );

it will not apply and the border will appear the same as the background color.

If the color is set using a separate border-color property, e.g.

border: 5px solid;
border-color: gradient( linear, 0% 0%, 100% 0%, from( #f1efe2 ), to( #716f64 ) )

This will result in a parsing error. (Ignore that it says linear-gradient, that was me trying something else and this was the only screenshot I had)

[craftablescience]

Since border color is defined to be a ... color, it would make more sense to make a border-image property that can accept gradients (maybe images too?) like its CSS counterpart

[vrad-exe]

Yeah probably, if that's what normal CSS does. I was expecting this to work because background-color accepts a gradient, though actually that's probably just acting as an alias for background-image.